Polyolefin compositions having high fluidity

ABSTRACT

A polyolefin composition suitable for preparing films and sheets, comprising: (A) from 15 to 40% by weight of a crystalline copolymer of propylene with at least one alpha-olefin of formula H 2 C═CHR 1 , where R 1  is H or a C 2-8  linear or branched alkyl, containing at least 90% by weight of propylene, having solubility in xylene at room temperature lower than 15% by weight; (B) from 60 to 85% by weight of an elastomeric fraction comprising: (1) a copolymer of propylene with ethylene, optionally containing 0.5 to 5% by weight of a diene, containing from 20 to 35% by weight ethylene, and having solubility in xylene at room temperature greater than 45% by weight, the intrinsic viscosity of the xylene soluble fraction ranging from 1.0 to 3.9 dl/g; and (2) a copolymer of ethylene with at least one alpha-olefin of formula H 2 C═CHR 2 , where R 2  is a C 2-8  linear or branched alkyl, optionally containing 0.5 to 5% by weight of a diene, containing 15% to 40% by weight alpha-olefin, and having solubility in xylene at room temperature greater than 35% by weight, the intrinsic viscosity of the xylene soluble fraction ranging, from 1.0 to 3.0 dl/g; the (1)/(2) weight ratio ranging from 1:5 to 5:1. The polyolefin composition of the invention, preferably prepared by sequential polymerization in at least three stages, has a flexural modulus lower than 130 Mpa, shore D hardness lower than 40, and MFR ≧1.5 g/10 min.

FIELD OF THE INVENTION

The present invention concerns polyolefin compositions having improvedfluidity, softness and free of gels, which can be advantageously usedfor producing films and sheets, and in particular cast films. Thesecompositions may be obtained by a sequential polymerization process.

PRIOR ART DISCLOSURE

Polyolefin compositions having elastic properties, as well as goodmechanical and optical properties have been used in many applicationfields, due to the characteristics which are typical of polyolefins(such as chemical inertia, mechanical properties and nontoxicity);moreover, these compositions show outstanding cost/performance ratios.

In the state of the art, elastic polypropylene compositions retaining agood mechanical behavior has been obtained by way of sequentialcopolymerization of propylene, optionally containing minor quantities ofolefin comonomers, and then ethylene/propylene or ethylene/alpha-olefinmixtures. Catalysts based on halogenated titanium compounds supported onmagnesium chloride are commonly used for this purpose.

For instance EP-A-400 333, in the name of the same Applicant, describeselastoplastic polyolefin compositions, obtained by sequentialpolymerization, comprising:

-   A) 10-60 parts by weight of a crystalline polymer or copolymer of    propylene;-   B) 10-40 parts by weight of a polymer fraction containing ethylene,    insoluble in xylene at room temperature; and-   C) 30-60 parts by weight of an ethylene/propylene copolymer    fraction, soluble in xylene at room temperature.

These compositions do not show satisfactory flexibility and elasticproperties, as demonstrated by the flexural modulus values (comprisedbetween 200 and 700 MPa); moreover, they do not have satisfactoryoptical properties, such as transparency.

EP-A-472 946, in the name of the same Applicant, describes flexiblepolyolefin compositions comprising, in parts by weight:

-   A) 10-50 parts of an isotactic propylene homopolymer or copolymer;-   B) 5-20 parts of an ethylene copolymer, insoluble in xylene at room    temperature; and-   C) 40-80 parts of an ethylene/propylene copolymer containing less    than 40% by weight of ethylene and being soluble in xylene at room    temperature; the intrinsic viscosity of said copolymer is preferably    from 1.7 to 3 dl/g.

These compositions have a flexural modulus of less than 150 MPa and aShore D hardness between 20 and 35. Although these mechanical propertiesare advantageous with respect to the compositions known in the priorart, and are relatively satisfactory for certain applications, theyexhibit very low fluidity values; in fact, the Melt Flow Rate (MFR)values of the disclosed polyolefin compositions are not higher than 1.5g/10 min (the Applicant measured the MFR values of the compositionsprepared in Examples 1-5 of the cited document, which resultedrespectively equal to 1.4, 1.0, 1.0, 0.8 and 1.0 g/10 min). Due to thesevalues (inferior to 1.5), for many applications, such as cast films, thepolymer does not show a sufficient fluidity and therefore is notprocessable with common techniques.

As it is well known in the art, the MFR values of polyolefincompositions may be enhanced by peroxide treatments; nevertheless, thistreatment causes various drawbacks, such as the yellowness of thepolymer, the formation gels and the release of bad odors during thesubsequent treatments. Moreover, in many countries, the productsobtained by visbreaking may not be used in food applications, such asfresh products packaging.

The European Patent Application No. 1202876.7, in the name of the sameApplicant, describes a polyolefin composition comprising:

-   (A) from 8 to 25% by weight of a crystalline propylene homopolymer    or copolymer; and-   (B) from 75 to 92% by weight of an elastomeric fraction comprising a    first elastomeric copolymer of propylene with 15-32% wt ethylene,    the intrinsic viscosity of the xylene soluble fraction ranging from    3.0 to 5.0 dl/g; and a second elastomeric copolymer of propylene    with more than 32% up to 45% wt. of ethylene, the intrinsic    viscosity of the xylene soluble fraction ranging from 4.0 to 6.5    dl/g.

These compositions have flexural modulus values lower than 60 M/Pa andvery good hardness values (Shore A hardness lower than 90);nevertheless, they exhibit very low fluidity. In fact, the polyolefincompositions described in the application show MFR values not higherthan 0.1 g/10 min. As reported above, such values are not satisfactoryfor many applications, such as cast films, and the peroxide treatment ofthese compositions to enhance the MFR would inevitably lead to gelsformation, yellowness of the final product, as well as to the release ofbad odors during the subsequent transformation.

Therefore, it is felt the need for polyolefin compositions, having highsoftness and good mechanical properties (such as hardness), at the sametime having an enhanced fluidity (i.e. high MFR values) without thepresence of gels and other negative effects due to peroxide treatments.

SUMMARY OF THE INVENTION

The present invention concerns a polyolefin composition comprising:

-   (A) from 15 to 40% by weight of a crystalline copolymer of propylene    with at least one alpha-olefin of formula H₂C═CHR¹, where R¹ is H or    a C₂₋₈ linear or branched alkyl, containing at least 90% by weight    of propylene, and having solubility in xylene at room temperature    lower than 15% by weight;-   (B) from 60 to 85% by weight of an elastomeric fraction comprising:    -   (1) a copolymer of propylene with ethylene, optionally        containing 0.5 to 5% by weight of a diene, containing from 20 to        35% by weight ethylene, and having solubility in xylene at room        temperature greater than 45% by weight, the intrinsic viscosity        of the xylene soluble fraction ranging from 1.0 to 3.0 dl/g; and    -   (2) a copolymer of ethylene with at least one alpha-olefin of        formula H₂C═CHR², where R² is a C₂₋₈ linear or branched alkyl,        optionally containing 0.5 to 5% by weight of a diene, containing        15% to 40% by weight alpha-olefin, and having solubility in        xylene at room temperature greater than 35% by weight, the        intrinsic viscosity of the xylene soluble fraction ranging from        1.0 to 3.0 dl/g; the (1)/(2) weight ratio ranging from 1:5 to        5:1.

The polyolefin composition of the invention, preferably prepared bysequential polymerization in at least three stages, has a flexuralmodulus ≦130 MPa, Shore D hardness ≦40, and MFR ≧1.5 g/10 min.

It is another object of the present invention a process for thepreparation of the polyolefin composition reported above, comprising atleast three sequential polymerization stages, with each subsequentpolymerization being conducted in the presence of the polymeric materialformed in the immediately preceding polymerization reaction, wherein thecrystalline copolymer (A) is prepared in a first stage, and theelastomeric fraction (B) is prepared in at least two subsequent stages.According to a preferred embodiment, all the polymerization stages arecarried out in the presence of a catalyst comprising a trialkylaluminumcompound, optionally an electron donor, and a solid catalyst componentcomprising a halide, or halogen-alcoholate of Ti, and an electron donorcompound supported on anhydrous magnesium chloride, said solid catalystcomponent having a surface area (measured by BET) of less than 200 m²/g,and a porosity (measured by BET) higher than 0.2 ml/g.

DETAILED DESCRIPTION OF THE INVENTION

The polyolefin compositions of the invention are endowed with highfluidity, as evidenced by MFR values ≧1.5 g/10 min, and are gel-free.Moreover, they exhibit a very good balance of softness and mechanicalproperties, and in particular of Flexural Modulus values and Shore Dhardness, at the same time retaining good elastomeric properties.

These polyolefin compositions comprise from 15 to 40% by weight,preferably from 20 to 35%, and even more preferably from 25 to 30% of acrystalline copolymer of propylene (A), and from 60 to 85% by weight,preferably from 65 to 80%, and even more preferably from 70 to 75% byweight of an elastomeric fraction (B).

The crystalline copolymer (A) of the compositions of the invention is acopolymer of propylene with an alpha-olefin H₂C═CHR¹, where R¹ is H or aC₂₋₈ linear or branched alkyl, containing at least 90% by weight ofpropylene, preferably at least 95% propylene. This copolymer hassolubility in xylene at room temperature lower than 15% by weight,preferably lower than 10%, and even more preferably lower than 8%. Saidalpha-olefin is preferably ethylene, 1-butene, 1-pentene,4-methylpentene, 1-hexene, 1-octene or combinations thereof, and evenmore preferably it is ethylene.

The elastomeric fraction (B) of the polyolefin compositions of theinvention comprises a copolymer of propylene with ethylene, and acopolymer of ethylene with an alpha-olefin H₂C═CHR², where R² is a C₂₋₈alkyl. By “elastomeric” is meant herein a polymer having lowcristallinity or amorphous, having a solubility in xylene at roomtemperature greater than 40% by weight.

The copolymer (1) of propylene with ethylene contains from 20 to 35% byweight of ethylene, preferably from 25 to 30%, and has a solubility inxylene at room temperature greater than 45% by weight, preferablygreater than 50%; the intrinsic viscosity of the xylene soluble fractionranges from 1.0 to 3.0 dl/g, and more preferably from 1.5 to 2.5 dl/g.

The copolymer (2) is a copolymer of ethylene with at least one alphaolefin of formula H₂C═CHR², where R² is a C₂₋₈ linear or branched alkyl,optionally containing 0.5 to 5% by weight of a diene; said alpha-olefinis preferably 1-butene, 1-hexene or 1-octene, and even more preferablyis 1-butene. The alpha-olefin content ranges from 15% to 40% by weight,and preferably from 20 to 35%. The copolymer (2) has solubility inxylene at room temperature greater than 35% by weight, preferablygreater than 40%, and the intrinsic viscosity of the xylene solublefraction ranges from 1.0 to 3.0 dl/g, preferably from 1.5 to 2.5 dl/c.

As previously reported, the copolymers (1) and (2) of the elastomericfraction (B) may contain a diene, conjugated or not, such as butadiene,1,4-hexadiene, 1,5-hexadiene and ethylidene-norbornene-1. The diene,when present, is contained in an amount of from 0.5 to 5% by weight,with respect to the weight of the fraction (B).

The weight ratio of the elastomeric copolymers (1)/(2) ranges from 1:5to 5:1, and preferably from 1:2 to 2:1.

The polyolefin composition of the invention has a flexural modulus ≦130MPa, and preferably ≦100 MPa; Shore D hardness ≦40, and preferablyranging from 25 to 35; and MFR ≧1.5 g/10 min, preferably ≧2.0 g/10 min,and even more preferably ≧3.0 g/10 min. According to a preferredembodiment of the invention, the polyolefin composition is in the formof spherical particles having an average diameter of 250 to 7,000microns, a flowability of less than 30 seconds and a bulk density(compacted) greater than 0.4 g/ml. The polyolefin composition of theinvention may be prepared by sequential polymerization in at least threestages; according to a preferred embodiment, the sequentialpolymerization is carried out in the presence of a catalyst comprising atrialkylaluminum compound, optionally an electron donor, and a solidcatalyst component comprising a halide or halogen-alcoholate of Ti, andan electron-donor compound supported on anhydrous magnesium chloride.

It is therefore another object of the present invention a process forthe preparation of the polyolefin compositions as reported above, saidprocess comprising at least three sequential polymerization stages witheach subsequent polymerization being conducted in the presence of thepolymeric material formed in the immediately preceding polymerizationreaction, wherein the crystalline copolymer (A) is prepared in at leastone first stage, and the elastomeric fraction (B) is prepared in atleast two sequential stages. The polymerization stages may be carriedout in the presence of a Ziegler-Natta and/or a metallocene catalyst.

Suitable Ziegler-Natta catalysts are described in U.S. Pat. No.4,399,054 and EP-A-45 977. Other examples can be found in U.S. Pat. No.4,472,524.

The solid catalyst components used in said catalysts comprise, aselectron-donors (internal donors), compounds selected from the groupconsisting of ethers, ketones, lactones, compounds containing N, Pand/or S atoms, and esters of mono- and dicarboxylic acids.

Particularly suitable electron-donor compounds are phtlialic acidesters, such as diisobutyl, dioctyl, diphenyl and benzylbutyl phthatate.

Other suitable electron-donors are 1,3-diethers of formula:

wherein R^(I) and R^(II), the same or different from each other, areC₁-C₁₈ alkyl, C₃-C₁₈ cycloalkyl or C₇-C₁₈ aryl radicals; R^(III) andR^(IV), the same or different from each other, are C₁-C₄ alkyl radicals;or are the 1,3-diethers in which the carbon atom in position 2 belongsto a cyclic or polycyclic structure made up of 5, 6 or 7 carbon atomsand containing two or three unsaturations.

Ethers of this type are described in EP-A-361 493 and EP-A-728 769.

Representative examples of said dieters are2-methyl-2-isopropyl-1,3-dimethoxypropane,2,2-diisobutyl-1,3-dimethoxypropane,2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane,2-isopropyl-2-isoamyl-1,3-dimethoxypropane, and9,9-bis(methoxymethyl)fluorene.

The preparation of the above mentioned catalyst components is carriedout according to various methods.

For example, a MgCl₂.nROH adduct (in particular in the form ofspheroidal particles) wherein n is generally from 1 to 3 and ROH isethanol, butanol or isobutanol, is reacted with an excess of TiCl₄containing the electron-donor compound. The reaction temperature isgenerally from 80 to 120° C. The solid is then isolated and reacted oncemore with TiCl₄, in the presence or absence of the electron-donorcompound, after which it is separated and washed with aliquots of ahydrocarbon until all chlorine ions have disappeared.

In the solid catalyst component the titanium compound, expressed as Ti,is generally present in an amount from 0.5 to 10% by weight. Thequantity of electron-donor compound which remains fixed on the solidcatalyst component generally is 5 to 20% by moles with respect to themagnesium dihalide.

The titanium compounds which can be used in the preparation of the solidcatalyst component are the halides and the halogen alcoholates oftitanium. Titanium tetrachloride is the preferred compound.

The reactions described above result in the formation of a magnesiumhalide in active form. Other reactions are known in the literature,which cause the formation of magnesium halide in active form startingfrom magnesium compounds other than halides, such as magnesiumcarboxylates.

The Al-alkyl compounds used as co-catalysts comprise Al-trialkyls, suchas Al-triethyl, Al-triisobutyl, Al-tri-n-butyl, and linear or cyclicAl-alkyl compounds containing two or more Al atoms bonded to each otherby way of O or N atoms, SO₄ or SO₃ groups. The Al-alkyl compound isgenerally used in such a quantity that the Al/Ti ratio be from 1 to1000.

The electron-donor compounds that can be used as external donors includearomatic acid esters such as alkyl benzoates, and in particular siliconcompounds containing at least one Si—OR bond, where R is a hydrocarbonradical.

Examples of silicon compounds are (tert-butyl)₂Si (OCH₃)₂,(cyclohexyl)(methyl)Si (OCH₃)₂, (phenyl)₂Si (OCH₃)₂ and (cyclopentyl)₂Si(OCH₃)₂. 1,3-diethers having the formulae described above can also beused advantageously. If the internal donor is one of these dieters, theexternal donors can be omitted.

The solid catalyst component have preferably a surface area (measured byBET) of less than 200 m²/g, and more preferably ranging from 80 to 170m²/g, and a porosity (measured by BET) preferably greater than 0.2 ml/g,and more preferably from 0.25 to 0.5 ml/g.

The catalysts may be precontacted with small quantities of olefin(prepolymerization), maintaining the catalyst in suspension in ahydrocarbon solvent, and polymerizing at temperatures from ambient to60° C., thus producing a quantity of polymer from 0.5 to 3 times theweight of the catalyst. The operation can also take place in liquidmonomer, producing, in this case, a quantity of polymer 1000 times theweight of the catalyst.

By using the above mentioned catalysts, the polyolefin compositions areobtained in spheroidal particle form, the particles having an averagediameter from about 250 to 7,000 microns, a flowability of less than 30seconds and a bulk density (compacted) greater than 0.4 g/ml.

Other catalysts that may be used in the process according to the presentinvention are metallocene-type catalysts, as described in U.S. Pat. No.5,324,800 and EP-A-0 129 368; particularly advantageous are bridgedbis-indenyl metallocenes, for instance as described in U.S. Pat. No.5,145,819 and EP-A-0 485 823. Another class of suitable catalysts arethe so-called constrained geometry catalysts, as described in EP-A-0 416815, EP-A-0 420 436, EP-A-0 671 404, EP-A-0 643 066 and WO 91/04257.These metallocene compounds may be used to produce the copolymers (1)and (2) of the elastomeric fraction (B).

According to a preferred embodiment, the polymerization process of theinvention comprises three stages, all carried out in the presence ofZiegler-Natta catalysts, where: in the first stage the relevantmonomer(s) are polymerized to form the crystalline copolymer (A); in thesecond stage a mixture of propylene and ethylene, and optionally a dieneare polymerized to form the copolymer (B) (1); and in the third stage amixture of ethylene and an alpha-olefin H₂C═CHR², where R² is a C₂₋₈alkyl, and optionally a diene, are polymerized to form the copolymer (B)(2).

The polymerization stages may occur in liquid phase, in gas phase orliquid-gas phase. Preferably, the polymerization of the crystallinecopolymer fraction (A) is carried out in liquid monomer (e.g. usingliquid propylene as diluent), while the copolymerization stages of thecopolymers (B)(1) and (B)(2) are carried out in gas phase, withoutintermediate stages except for the partial degassing of the propylene.According to a most preferred embodiment, all the three sequentialpolymerization stages are carried out in gas phase.

The reaction temperature in the polymerization stage for the preparationof the crystalline copolymer (A) and in the preparation of thecopolymers (B)(1) and (B)(2) can be the same or different, and ispreferably from 40° C. to 90° C.; more preferably, the reactiontemperature ranges from 50 to 80° C. in the preparation of the fraction(A), and from 40 to 80° C. for the preparation of components (B)(1) and(B)(2).

The pressure of the polymerization stage to prepare the fraction (A), ifcarried out in liquid monomer, is the one which competes with the vaporpressure of the liquid propylene at the operating temperature used, andis possibly modified by the vapor pressure of the small quantity ofinert diluent used to feed the catalyst mixture, and the overpressure ofthe monomers and the hydrogen optionally used as molecular weightregulator.

The polymerization pressure preferably ranges from 33 to 43 bar, if donein liquid phase, e and from 5 to 30 bar if done in gas phase. Theresidence times relative to the three stages depend on the desired ratiobetween the fractions, and can usually range from 15 minutes to 8 hours.Conventional molecular weight regulators known in the art, such as chaintransfer agents (e.g. hydrogen or ZnEt₂), may be used.

The polyolefin compositions of the present invention find application inthe preparation of films and sheets, and in particular of cast films. Infact, they possess a high fluidity, without the need of peroxidetreatments. Moreover, they show a good balance of softness andmechanical properties, and retain acceptable optical properties.

In cast films, which are often a multilayer structure with PE or otherpolymer films, the polyolefin compositions of the present inventionimprove the sealing of the skin and the core layers, thus avoidingdelamination problems.

Other possible applications of the gel free polyolefin compositions ofthe present invention, having high MFR values and high softness, are inelectric and electronic appliances with soft touch surfaces produced byinjection moulding, in particular for handles and grips; for producingrests handles by injection moulding; for producing fibres with improvedelasticity, softness and sealability, maintaining good spinning; and inmedical tubing.

The compositions of the invention may be used in combination with otherelastomeric polymers, such as ethylene/propylene copolymers (EPR),ethylene/propylene/diene terpolymers (EPDM), copolymers of ethylene withC₄-C₁₂ alpha-olefins (e.g. ethylene/octene-1 copolymers, such as theones commercialized under the name Engage®) and mixtures thereof. Suchelastomeric polymers may be present in an amount of 5 to 80% by weighton the total composition.

Conventional additives, fillers and pigments, commonly used in olefinpolymers, may be added, such as nucleating agents, extension oils,mineral fillers, and other organic and inorganic pigments.

The following analytical methods have been used to determine theproperties reported in the detailed description and in the examples.

Property Method Melt Flow Rate (MFR) ISO 1133 Ethylene % by weight I.R.Spectroscopy 1-Butene % by weight I.R. Spectroscopy Intrinsic ViscosityIn tetrahydronaphthalene, at 135° C. Flexural modulus at 23° C. ASTMD730M (3 hours) Shore Hardness D ASTM D 2240 Tensile strength at breakand at yield ASTM D 638 (3 hours) Elongation at break and at yield ASTMD 638 (3 hours) Haze ASTM D 1003 (100 micron film) Surface area B.E.T.Porosity B.E.T. Bulk density DIN 53194Determination of Xylene Solubility at Room Temperature (% by Weight):

2.5 g of polymer were dissolved in 250 ml of xylene, at 135° C., underagitation. After 20 minutes, the solution was cooled to 25° C. understirring, and then it was allowed to settle for 30 minutes.

The precipitate was filtered with filter paper; the solution wasevaporated under a nitrogen current, and the residue dried under vacuumat 80° C. until reached constant weight. The weight percentage ofpolymer soluble in xylene at room temperature was then calculated. Thepercent by weight of polymer insoluble in xylene at room temperature wasconsidered the isotactic index of the polymer. This value correspondedsubstantially to the isotactic index determined by extraction withboiling n-heptane, which by definition constitutes the isotactic indexof polypropylene.

Unless otherwise specified, the samples to be subjected to the variousphysical-mechanical analyses were molded by use of a Negri & Bossiinjection press 90, after stabilizing the sample with IRGANOX R 1010hindered phenolic stabilizer (0.05% by weight), and Q IRGAFOS 168phosphite stabilizer (0.1% by weight), and pelletizing the sample with atwin-screw Berstorff extruder (barrel diameter 25 mm) at 210° C.

The conditions were as follows:

-   -   temperature of the melt: 220° C.;    -   temperature of the mold: 60° C.;    -   injection time: 9 sec;    -   cooling time: 15 sec.

The dimensions of the plaques for the tests were 127×127×2.5 mm. Fromthese plaques, C-type dumbbells were cut and submitted to tensilestrength tests with a head speed of 500 mm/min. Also the specimens forthe flexural modulus and hardness Shore D were cut from these plaques.All the specimens were cut parallel to the advancement front andconsequently perpendicular to the flow direction.

EXAMPLES 1-6 Preparation of the Catalyst System

A catalyst component comprising MgCl₂.3C₂H₅OH adduct was prepared asfollows: 28.4 g of anhydrous MgCl₂, 49.5 g of pure anhydrous ethanol,100 ml of ROL OB/30 vaseline oil, and 100 ml of silicone oil (350 csviscosity) were introduced in a flask immersed in a baththermoregulated, at 120° C. under agitation, in an inert atmosphere,until the MgCl₂ was completely dissolved. The mixture was thentransferred hot, always under an inert atmosphere, in a 150 ml containerequipped with a heating jacket, and containing 150 ml of vaseline oiland 150 ml of silicone oil. The mixture was maintained at 120° C. andunder agitation, the latter being carried out with a Hanke & Kunkel K.G. Ika Werke Ultra Turrax T-45 N agitator. Said agitation continued for3 minutes at 3000 rpm. The mixture was discharged into a 2 liter vesselcontaining 1000 ml of anhydrous n-heptane stirred and cooled so that thefinal temperature did not exceed 0° C. The MgCl₂.3EtOH microspheres thusobtained were filtered and dried under vacuum at room temperature. Thedried adduct obtained in this manner was then dealcoholated by heatingat temperatures gradually increasing from 50° C. to 100° C., undernitrogen current, until the alcohol content was 1.1 moles per moleMglC₂.

The partially dealcoholated adduct thus obtained had a surface area of11.5 m²/g, a porosity of 0.13 and bulk density of 0.564 g/cc.

25 g of the obtained adduct were added, under stirring at 0° C., to 625ml of TiCl₄. The mixture was then heated to 100° C. in 1 hour. When thetemperature reached 40° C., diisobutylphthalate was added in an amountsuch that the Mg/diisobutylphtahalate molar ratio was 8. The resultingmixture was heated at 100° C. for 2 more hours, then allowed to settle,and the liquid was siphoned off hot. 550 ml of TiCl₄ were added and themixture was heated at 120° C. for 1 hour.

The obtained mixture was allowed to settle and the liquid was siphonedoff hot. The solid was washed 6 times using 200 ml of anhydrous hexaneat 60° C., and three more times using 200 ml of anhydrous hexane at roomtemperature.

After drying under vacuum, the solid presented porosity equal to 0.383ml/g and surface area equal to 150 m²/g.

General Polymerization Process

The polymerizations were done in stainless steel fluidized bed reactors.

During the polymerization, the gas phase in each reactor wascontinuously analyzed by gaschromatography in order to determine thecontent of ethylene, propylene and hydrogen. Ethylene, propylene,1-butene and hydrogen were fed in such a way that during the course ofthe polymerization their concentration in gas phase remained constant,using instruments that measure and/or regulate the flow of the monomers.

The operation was continuous in three stages, each one comprising thepolymerization of the monomers in gas phase.

Propylene was prepolymerized in liquid propane in a 75 liters stainlesssteel loop reactor with an internal temperature of 20-25° C. in thepresence of a catalyst system comprising a solid component (15-20 g/h)prepared as described above, and a mixture of 75-80 g/h Al-triethyl(TEAL) in a 10% hexane solution and an appropriate quantity ofdicyclopenthyldimethoxysilane (DCPMS) donor, so that the TEAL/DCPMS wt.ratio was 5. The catalyst was prepared according to the process reportedabove.

1st stage—The thus obtained prepolymer was discharged into the first gasphase reactor, having a temperature of 60° C. and a pressure of 14 bar.Thereafter, hydrogen, propylene, ethylene and an inert gas were fed inthe ratio and quantities reported in Table 1, to obtain the compositionof the gas phase reported in Table 1, and the polymerization was carriedout for 27 minutes.2nd stage—After removing a sample to carry out the various analyses, thepolymer obtained from the first stage was discharged into the secondphase reactor having a temperature of 60° C. and a pressure of 18 bar.Thereafter, hydrogen, propylene, ethylene and an inert gas were fed inthe ratio and quantities reported in Table 1, to obtain the compositionof the gas phase reported in Table 1, and the polymerization was carriedout for 23 minutes.3rd stage—After removing a sample to carry out the various analyses, thepolymer obtained from the second stage was discharged into the thirdphase reactor, having a temperature of 70° C. and a pressure of 14 bar.Thereafter, hydrogen, ethylene, 1-butene and an inert gas were fed inthe ratio and quantities reported in Table 1, to obtain the compositionof the gas phase reported in Table 1, and the polymerization was carriedout for the time reported in Table 1.

At the end of the polymerization, the particulate polymer wasdischarged, at atmospheric pressure, into a vessel where acountercurrent steam was fed in order to strip the remaining monomers.Thereafter, the polymer was discharged into a vessel, wherecountercurrent nitrogen was fed at 80-90° C. in order to dry thepolymer.

The operating conditions used in the above process and the results ofthe analyses performed on the polymer compositions obtained therefromare shown in Tables 1 and 2 respectively.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 1st stage (gas phase) Split(% wt.) 29 28 28 27 27 26 H₂ in gas phase (% mol) 5.9 5.9 5.9 6.2 6.26.2 Ethylene in gas phase (% mol) 0.7 0.7 0.7 0.7 0.7 0.7 Propylene ingas phase (% mol) 23.9 23.9 23.9 22.5 22.5 22.5 Ethylene in (A) (% wt)3.6 3.4 3.4 3.4 3.5 3.5 MFR “L” (g/10 min) 74 86 82 74 77 85 Sol. Xyl.(% wt) 6.0 6.0 6.0 6.0 6.0 6.1 2nd stage (gas phase) Split (% wt) 35 4040 39 38 35 H₂ in gas phase (% mol) 2.7 2.7 2.7 2.9 2.9 2.9 Ethylene ingas phase (% mol) 8.9 8.9 8.9 8.6 8.6 8.6 Propylene in gas phase (% mol)48.5 48.5 48.5 47.6 47.6 47.6 Ethylene in (B)(1) (% wt) 30 25 24 24 2425 Ethylene tot. (% wt) 18.3 15.5 14.7 15.1 14.5 14.5 MFR “L” tot. (g/10min) 6.8 5.7 7.8 n.d. n.d. n.d. Sol. Xyl. in (B)(1) (% wt) 89 85 83 n.d.83 n.d Sol. Xyl. tot. (% wt) 50.9 52.7 51.7 n.d. 50.7 n.d. I.V. Sol.Xyl. (dl/g) 2.37 2.24 2.32 2.25 2.28 n.d 3rd stage (gas phase) Split (%wt) 36 32 32 36 35 39 Time (minutes) 115 115 115 98 98 98 H₂ in gasphase (% mol) 9.9 9.9 9.9 11.1 11.1 11.1 Ethylene in gas phase (% mol)31.6 31.6 31.6 31.0 31.0 31.0 1-Butene in gas phase (% mol) 32.7 32.732.7 32.8 32.8 32.8 1-Butene in (B)(2) (% wt) 21 22 22 24 24 25 Sol.Xyl. in (B)(2) (% wt) 40 42 42 44 46 54 I.V. Sol. Xyl. (B)(2)(dl/g) 2.372.02 1.92 1.78 1.64 n.d.

TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 MFR “L” (g/10 min) 2.5 3.03.4 3.4 2.9 3.1 Sol. Xyl. (% wt) 46.8 48.8 48.6 n.d. 49.4 52.0 Ethylenecontent (% wt.) 39.9 35.6 35.4 37.1 37.7 39.8 1-Butene content (% wt.)7.5 7.4 6.9 8.3 8.8 9.7 I.V. Sol. Xyl. (dl/g) 2.37 2.18 2.21 2.10 2.07n.d. Flexural Modulus (MPa) 82 107 110 98 100 94 Tensile Strength atBreak (MPa) 13.8 16.3 17.0 15.9 15.2 15.5 Tensile Strength at Yield(MPa) 5.9 7.1 7.1 6.7 6.5 6.5 Elongation at Break (MPa) 880 940 960 960900 980 Elongation at Yield (MPa) 40.9 39.5 41.1 41.8 37.3 41.3 HardnessShore D (°S) 29.5 33.0 33.0 33.0 35.1 30.5 Haze (%) 72.5 47.2 16.7 44.638.5 36.5

1. A polyolefin composition comprising: (A) from 15 to 40% by weight ofa crystalline propylene copolymer comprising at least 90% by weight ofpropylene and at least one alpha-olefin of formula H₂C═CHR¹, where R¹ isH or a C₂₋₈ linear or branched alkyl, the crystalline propylenecopolymer comprising a solubility in xylene at room temperature lowerthan 15% by weight; (B) from 60 to 85% by weight of an elastomericfraction comprising: (1) a propylene and ethylene copolymer comprisingfrom 20 to 35% by weight of ethylene, the propylene and ethylenecopolymer comprising a solubility in xylene at room temperature greaterthan 45% by weight, and a xylene soluble fraction of the propylene andethylene copolymer comprising an intrinsic viscosity intetrahydronaphthalene at 135° C. ranging from 1.0 to 3.0 dl/g; and (2)an ethylene copolymer comprising 15 to 40% by weight of at least onealpha-olefin of formula H₂C═CHR², where R² is C₂₋₈ linear or branchedalkyl, the ethylene copolymer comprising a solubility in xylene at roomtemperature greater than 35% by weight, and a xylene soluble fraction ofthe ethylene copolymer comprising an intrinsic viscosity intetrahydronaphthalene at 135° C. ranging from 1.0 to 3.0 dl/g; wherein aweight ratio of B(1) to B(2) ranges from 1:5 to 5:1.
 2. The polyolefincomposition according to claim 1, wherein the propylene and ethylenecopolymer additionally comprises 0.5 to 5% by weight of a diene.
 3. Thepolyolefin composition according to claim 1, wherein the ethylenecopolymer additionally comprises 0.5 to 5% by weight of a diene.
 4. Thepolyolefin composition according to claim 1, wherein the crystallinepropylene copolymer ranges from 20 to 35% by weight.
 5. The polyolefincomposition according to claim 1, wherein the crystalline propylenecopolymer comprises at least 95% by weight of propylene and thesolubility in xylene at room temperature is lower than 10% by weight. 6.The polyolefin composition according to claim 1, wherein the at leastone alpha-olefin in the crystalline propylene copolymer is ethylene. 7.The polyolefin composition according to claim 1, wherein the propyleneand ethylene copolymer comprises from 25 to 30% by weight of ethylene,the propylene and ethylene copolymer comprising a solubility in xyleneat room temperature greater than 50% by weight, and the xylene solublefraction of the propylene and ethylene copolymer comprises an intrinsicviscosity in tetrahydronaphthalene at 135° C. ranging from 1.5 to 2.5dl/g.
 8. The polyolefin composition according to claim 1, wherein theethylene copolymer comprises from 20 to 35% by weight of at least onealpha-olefin, the ethylene copolymer comprising a solubility in xyleneat room temperature greater than 40% by weight, and the xylene solublefraction of the ethylene copolymer comprises an intrinsic viscosity intetrahydronaphthalene at 135° C. ranging from 1.5 to 2.5 dl/g.
 9. Thepolyolefin composition according to claim 1, wherein the at least onealpha-olefin in the ethylene copolymer is 1-butene, 1-hexene, or1-octene.
 10. The polyolefin composition according to claim 1 furthercomprising a flexural modulus ≦130 MPa, a Shore D hardness ≦40, and aMFR ≧1.5 g/10 min.
 11. The polyolefin composition according to claim 8,wherein the flexural modulus is ≦100 MPa, the Shore D hardness rangesfrom 25 to 35, and the MFR is ≧2.0 g/10 min.
 12. The polyolefincomposition according to claim 1, wherein the polyolefin composition isobtained by sequential polymerization in at least three stages carriedout in presence of a catalyst comprising a trialkylaluminum compound anda solid catalyst component comprising a halide or halogen-alcoholate ofTi and an electron-donor compound supported on anhydrous magnesiumchloride.
 13. The polyolefin composition according to claim 12, whereinthe catalyst further comprises an electron donor.
 14. A process forpreparing a polyolefin composition comprising: (A) from 15 to 40% byweight of a crystalline propylene copolymer comprising at least 90% byweight of propylene and at least one alpha-olefin of formula H₂C═CHR¹,where R¹ is H or a C₂₋₈ linear or branched alkyl, the crystallinepropylene copolymer comprising a solubility in xylene at roomtemperature lower than 15% by weight; (B) from 60 to 85% by weight of anelastomeric fraction comprising: (1) a propylene and ethylene copolymercomprising from 20 to 35% by weight of ethylene, the propylene andethylene copolymer comprising a solubility in xylene at room temperaturegreater than 45% by weight, and a xylene soluble fraction of thepropylene and ethylene copolymer comprising an intrinsic viscosity intetrahydronaphthalene at 135° C. ranging from 1.0 to 3.0 dl/g; and (2)an ethylene copolymer comprising 15 to 40% by weight of at least onealpha-olefin of formula H₂C═CHR², where R² is C₂₋₈ linear or branchedalkyl, the ethylene copolymer comprising a solubility in xylene at roomtemperature greater than 35% by weight, and a xylene soluble fraction ofthe ethylene copolymer comprising an intrinsic viscosity intetrahydronaphthalene at 135° C. ranging from 1.0 to 3.0 dl/g; wherein aweight ratio of B(1) to B(2) ranges from 1:5 to 5:1, and the processcomprises at least three sequential polymerization stages with eachsubsequent polymerization stage being conducted in presence of apolymeric material formed in a immediately preceding polymerizationreaction, wherein the crystalline propylene copolymer is prepared in atleast one first stage and the elastomer fraction is prepared in at leasttwo sequential stages, wherein the at least three sequentialpolymerization stages are carried out in presence of a catalystcomprising a trialkylaluminum compound and a solid catalyst componentcomprising a halide or halogen-alcoholate of Ti and an electron-donorcompound supported on anhydrous magnesium chloride, the solid catalystcomponent comprising a surface area (measured by BET) of less than 200m²/g, and a porosity (measured by BET) greater than 0.2 ml/g.
 15. Theprocess for preparing a polyolefin composition according to claim 14,wherein the catalyst further comprises an electron donor.
 16. Theprocess according to claim 14, wherein the at least three sequentialpolymerization stages are all carried out in gas phase.
 17. A film,sheet, or mixture thereof comprising a polyolefin compositioncomprising: (A) from 15 to 40% by weight of a crystalline propylenecopolymer comprising at least 90% by weight of propylene and at leastone alpha-olefin of formula H₂C═CHR¹, where R¹ is H or a C₂₋₈ linear orbranched alkyl, the crystalline propylene copolymer comprising asolubility in xylene at room temperature lower than 15% by weight; (B)from 60 to 85% by weight of an elastomeric fraction comprising: (1) apropylene and ethylene copolymer comprising from 20 to 35% by weight ofethylene, the propylene and ethylene copolymer comprising a solubilityin xylene at room temperature greater than 45% by weight, and a xylenesoluble fraction of the propylene and ethylene copolymer comprising anintrinsic viscosity in tetrahydronaphthalene at 135° C. ranging from 1.0to 3.0 dl/g; and (2) an ethylene copolymer comprising 15 to 40% byweight of at least one alpha-olefin of formula H₂C═CHR², where R² is aC₂₋₈ linear or branched alkyl, the ethylene copolymer comprising asolubility in xylene at room temperature greater than 35% by weight, anda xylene soluble fraction of the ethylene copolymer comprising anintrinsic viscosity in tetrahydronaphthalene at 135° C. ranging from 1.0to 3.0 dl/g; wherein a weight ratio of B(1) to B(2) ranges from 1:5 to5:1.
 18. A cast film comprising a polyolefin composition comprising: (A)from 15 to 40% by weight of a crystalline propylene copolymer comprisingat least 90% by weight of propylene and at least one alpha-olefin offormula H₂C═CHR¹, where R¹ is H or a C₂₋₈ linear or branched alkyl, thecrystalline propylene copolymer comprising a solubility in xylene atroom temperature lower than 15% by weight; (B) from 60 to 85% by weightof an elastomeric fraction comprising: (1) a propylene and ethylenecopolymer comprising from 20 to 35% by weight of ethylene, the propyleneand ethylene copolymer comprising a solubility in xylene at roomtemperature greater than 45% by weight, and a xylene soluble fraction ofthe propylene and ethylene copolymer comprising an intrinsic viscosityin tetrahydronaphthalene at 135° C. ranging from 1.0 to 3.0 dl/g; and(2) an ethylene copolymer comprising 15 to 40% by weight of at least onealpha-olefin of formula H₂C═CHR², where R² is a C₂₋₈ linear or branchedalkyl, the ethylene copolymer comprising a solubility in xylene at roomtemperature greater than 35% by weight, and a xylene soluble fraction ofthe ethylene copolymer comprising an intrinsic viscosity intetrahydronaphthalene at 135° C. ranging from 1.0 to 3.0 dl/g; wherein aweight ratio of B(1) to B(2) ranges from 1:5 to 5:1.